Hitherto, a sheet finisher is known which is disposed downstream of an image forming apparatus such as a copier, a printer, or a multi-functional peripheral (MFP) and performs finishing such as punching or stitching on printed sheets.
Recently, functions of a sheet finisher are diversified, and a sheet finisher (sheet folding apparatus) is developed which has, in addition to the punching and stitching functions, a folding function of folding a part of a sheet, or a saddle-stitching and folding function of stitching the center of a sheet with staples and then folding the sheet at the center (see JP-A 2004-106991, U.S. Pat. No. 6,905,118, etc.).
A sheet folding apparatus having the saddle-stitching and folding function can form a booklet (bind a book) from plural printed sheets.
In the saddle-stitching and folding hitherto developed, the center of sheets is stitched with staples or the like and then the stitched portion is creased and folded by a pair of rollers called fold rollers. In this process, a plate-like member called a folding blade is applied to the stitched portion of the sheet bundle and is pushed into a nipping portion of the fold roller pair to crease the sheet bundle.
To form an excellent fold, the folding blade is usually formed of a very thin metal plate and thus the folding blade has a sharp edge.
In the meantime, a paper jam may occur in the nipping portion of the fold roller pair or in the vicinity thereof due to some reasons in the course of performing the folding function.
When the paper jam occurs, the movement of the fold roller pair and the folding blade is automatically stopped. Thereafter, a user accesses a position where the paper jam occurs and removes the sheet bundle. The method of removing sheets depends on the position of the paper jam or the status of the paper jam.
When the paper jam occurs such that the sheet bundle is exposed to the outside of the fold roller pair, for example, the fold roller pair is manually rotated to forcibly push out the jammed sheet bundle to the outside (in the conveyance direction) of the fold roller pair. Alternatively, the fold roller pair pressed to each other is manually separated temporarily and the sheet bundle nipped in the nipping portion of the fold roller pair is pulled out to the outside (in the conveyance direction) of the fold roller pair.
In contrast, when the sheet bundle is not exposed to the outside of the fold roller pair and the sheet bundle can not be pushed out to the outside of the fold roller pair even with the manual rotation of the fold roller pair, the user must access the inside (the opposite direction of the conveyance direction) of the fold roller pair and remove the sheet bundle.
The folding blade is placed inside the fold rollers and the edge of the folding blade is sharp as described above. Accordingly, when the user's finger, etc. carelessly approaches the nipping portion or the vicinity thereof in the fold roller pair, the user's finger, etc. may be injured with the edge of the folding blade.